This invention relates to electrical appliance control within a building and has particular application to appliance control within a domestic building.
Conventionally, electrical appliance control within a building is achieved simply by the use of the existing power main together with switches at fixed locations and switches on the appliances. Remote control is not conventionally available other than by use of the switches at the fixed locations and, in recent times, by an ultrasonic link directly to a specific appliance, such as a television receiver. The problem exists, therefore, of providing for a more flexible remote control of electrical appliances in a building. According to the invention, a solution to this problem resides in the use of control signals supplied to the appliances via the power main.
Control systems have been disclosed in the prior art (so-called ripple control systems) in which devices such as recording meters, security systems and street lamps can be controlled from remote transmitters permanently connected to the power supply system supplying such devices. It appears that such systems have been used only for public utilities, such as electricity boards, and are not suitable for domestic use.